1. Field of the Invention
The invention relates generally to equalizer bar assemblies for use with various track-type vehicles for various works including, but not limited to, construction, civil engineering, and agricultural works. More specifically, the invention relates to an equalizer bar for implementing improvements of a track-type vehicle in ride quality, work efficiency, traveling stability, and the like.
2. Related Art
Work vehicles for carrying out various works such as construction and civil engineering works are driven to travel over soft and hard ground including mud, crashed stone debris, and the like. In addition, the vehicle is driven to travel over soft and hard ground such as unleveled ground including sharp slopes and continually irregular surfaces. As such, the work vehicles have track-type roller assemblies supported to be oscillatorily movable in right and left portions of the vehicle body via pivot shafts and an equalizer bar. Since the individual track-type roller assemblies are thus supported to the vehicle body via the pivot shafts and the equalizer bar, the vehicle body weight and the vertical loads imposed during travel of the vehicle over rough ground such as continually-irregular unleveled ground are commonly supported by the pivot shafts and the equalizer bar.
In general, the pivot shafts are provided in rearward portions of the vehicle body and are disposed there to protrude to two opposing sides in the vehicle-body width direction. The individual track frames of the track-type roller assemblies are each connected to be oscillatorily movable in the vertical direction about an axial portion of the pivot shaft in the rotational center. A central portion of the equalizer bar is supported to be oscillatorily movable in a forward side of the vehicle body through pins protrusively provided in a forward portion of the vehicle body in a direction perpendicular to the track frames. Both the right and left portions of the equalizer bar are rotationally connected to the individual track frames (such construction is disclosed in U.S. Pat. No. 5,358,064).
During the travel of the track-type vehicle over a continually-irregular unleveled ground, the track frames oscillatorily move in the vertical direction about the pivot shaft in the rotational center along the geometrical shape.
In line with the vertical oscillatory movement of the track frames, the equalizer bar oscillatorily moves in right and left directions perpendicular to the individual track frames about the axial portions of the pins in the rotational centers. When the equalizer bar oscillatorily moves greater than necessary, since end portions thereof strongly collide with the vehicle body, there arise problems in that oscillatory movements, oscillations, and the like of the vehicle body are also greater than necessary.
To solve the problems described above, the conventional track-type vehicle has an elastomeric bumper pad between the vehicle body and the equalizer bar. Thereby, even when the track-type vehicle oscillates greatly, the equalizer bar and the vehicle body mutually absorb the oscillatory shocks via the elastomeric pad not to directly collide with each other. In this manner, the vehicle regulates the oscillatory movements of the equalizer bar.
Nevertheless, however, similar to the equalizer bar disclosed in the specification of the U.S. Patent referenced above, conventional equalizer bars are formed of a lengthy cast block body having very high stiffness. As such, the conventional equalizer bars almost do not have a buffering function that serves during travel of the track-type vehicle. Because of the structural characteristics, when travel-time external forces such as oscillations and shocks transmitted from ground-engagement portions cannot be sufficiently absorbed, the characteristics such as ride quality and traveling stability are significantly degraded. This consequently causes fatigue of an operator to be increased, potentially leading to creation of the cause of disturbing safety operation.
The equalizer bar is formed of the block body longer than the width of the vehicle body. This entails increased outer dimensions of the equalizer bar, thereby increasing the weight of the vehicle. In addition, although the equalizer bar is formed of a material such as Si—Mn cast steel having high stiffness, the material is expensive.
A central portion of the equalizer bar is pin-connected to the vehicle body, and is thereby supported to be oscillatorily movable in the direction perpendicular to the individual track frames. However, in such a supporting structure of the equalizer bar, the rotational movement about the pins frequently exerts excessive forces on the pin-connected portions. This can make deformation, wear, damage, and/or the like to easily occur in the pin-connected portions, consequently arising additional a problem in durability.